By all accounts, it was a freak accident that shattered Louisville Cardinal Kevin Ware’s lower right leg in an NCAA regional championship game. But what makes young bone so vulnerable to such breaks?

On Sunday night, sophomore guard Ware underwent a successful two-hour surgery to re-set his broken bone at Methodist Hospital in Indianapolis. Hours before, Ware leaped to contest a three-point shot during the NCAA Midwest Regional championships and landed like a piece of glass, breaking his tibia practically on impact and shooting a piece of the split bone through his shin.

The injury startled players and fans on both teams, some to tears, as emergency medical personnel quickly moved to cover the injury with towels.

University of Louisville announced in a press release that Ware’s two-hour surgery went smoothly, and the Associated Press reported he was walking, carefully, and ready to join his team in Atlanta for the Final Four. His bone was set, the wound was closed, and a rod was inserted in his right tibia, where it will remain to stabilize the bone and serve as a buttress during healing. Ware continued to stay positive despite his injury, even telling his teammates to “win the game, win the game,” which they did, 85-63.

Ware’s profound injury is highly unusual in basketball players, with some experts referring to it as a “freak accident.” “It’s not a common injury we see in the sports setting at all. We usually see this from car accidents or traumatic falls from very significant heights, where there is enough force for the bone to shatter and come through the skin in a compound-like fracture,” says Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York City and a former sideline physician for the New York Jets.

A compound fracture is a break that’s severe enough to puncture through skin. Because the bone, normally protected within the body, is exposed to bacteria and other debris and contaminants in the air, these breaks are more likely to cause infections that, if left untreated, could become fatal. That’s why Ware was treated with antibiotics and rushed to surgery soon after the injury.

How did the bones in the leg, presumably strong enough to withstand considerable force, buckle under Ware’s own weight? “He probably torqued his leg, or slightly rotated it so that when he landed, the force transmitted through the bone and punctured the skin,” says Glatter. Such a scenario is simply unlucky chance and not likely to occur often. However, there are a few other factors that can contribute to such breaks in well-trained athletes, that aren’t caused by enormous amounts of force packed into normal collisions or falls that can occur during play. A prior, and much smaller, injury like a stress fracture that could have left his tibia weaker may have made Ware more vulnerable to a fracture. “He probably had a pre-existing stress fracture or some inherent weakness in the bone. It’s unlikely this was a normal bone. People go up all the time and block shots,” says Glatter. Ware’s coach Rick Pitino told AP, however, that there was “nothing prior” to put him at risk.

Endurance athletes often harbor stress fractures in their bones, especially in their lower extremities, that result from overuse. However, this type of silent fracture is more common among professional runners, like American Olympic athlete Manteo Mitchell, who ran with a broken leg in a qualifying heat during the London 2012 Olympics. Mitchell had apparently slipped on the stairs in the athletes’ village several days before the race, but felt his left fibula pop as he rounded the last lap of the men’s 4 x 400-m preliminary relay. “Could [a similar stress fracture] have contributed to someone who has been running extensively [up and down the basketball court] for the length of an entire season? It’s possible. [But] it’s not a usual problem in a basketball player,” says Dr. Timothy Hewett of the Ohio State University Wexner Medical Center.

Hewett says other contributing factors could be related to bone density, diet and vitamin D levels. Every year, Hewett measures the bone density of members of the Ohio State Football team prior to their season. He also tests the vitamin D levels of each athlete and screens them for nutritional deficiencies — all to help prevent broken bones in the coming, often punishing season. Recent studies showed that most Americans have low levels of vitamin D, in part because they spend more time indoors and don’t take advantage of the natural synthesis of vitamin D when skin is exposed to the sun’s rays. “If vitamin D levels are low, which they tend to be in the Midwest, we supplement. We also see whether a person is getting efficient calcium from their diet,” says Hewett. “Even well-trained athletes still have diet deficiencies. Just for the football team we have two nutritionists on staff. It is definitely a factor in high school and college athletes.”

Poor diet may also play a role in weaker bones, particularly among younger kids, with some researchers suggesting that children drinking too much soda or not eating enough vitamin-rich foods are vulnerable to brittler and thinner bones.

There are also genetic conditions and bone diseases that can make the skeleton more vulnerable to fractures, although it’s not likely that such individuals would be able to endure the physical punishment of training at such an elite level as Ware and other athletes.

Despite the severity of the break, given that Ware is otherwise healthy and young, he may be able to play next season, although the recovery will be long. “This type of injury could take three to six months to heal for someone who is healthy without significant medical problems, especially an athlete. But ultimate healing and remolding can take up to a year,” says Glatter, depending on how badly surrounding tissues and nerves were damaged in the trauma.

“I don’t know the exact nature of his injury, but there could also be nerve damage. When you have such a traumatic injury, you can also injure nerves that are functional to muscles as well as sensations to the skin.” says Glatter. “High-performing athletes need to have full function, which means twisting, pivoting and having full sensations and position as they move across the court.” To return him to playing shape, Ware’s therapy will likely be aggressive.

As the Louisville Cardinals seek to climb to the top of the NCAA bracket, Ware is hoping that an NCAA trophy will help motivate him through that recovery. But in the meantime, he also has at least one happy memento from the Midwest championship game — the regional trophy. The prize greeted Ware when he woke up from surgery, and Pitino said Ware would hold on to it, for now.